In recent years, there have been proposed and developed various automated manual transmissions, each of which employs a mechanism by which gear shifting is automated instead of manual gear shifting action (manual clutch operation) by the driver. One such automated manual transmission has been disclosed in Japanese Patent Provisional Publication No. 2007-040408 (hereinafter is referred to as “JP2007-040408”), assigned to the assignee of the present invention. In the case of an automated manual transmission, often abbreviated to “AMT”, disclosed in JP2007-040408, due to the occurrence of an AMT system failure that an automatic clutch remains engaged undesirably, there is a risk of stalling an engine under an abnormal state where the AMT is unable to shift into neutral.
In such an abnormal state (i.e., with the automatic clutch remaining engaged), during the next engine starting period, the engine would be started up in a state where the AMT remains thrown into a certain shift stage (a certain range gear position). This state will be hereinafter referred to as “starting-period shift-stage thrown state”. Thus, the AMT as disclosed in JP2007-040408 suffers from the following drawbacks.
Suppose that the previously-discussed AMT system failure that an automatic clutch remains engaged undesirably does not occur. Under such a normal state (i.e., in the absence of the AMT system failure), even when starting up the engine in a state where the AMT remains thrown into a certain shift stage, the automatic clutch can be released by using working oil discharged from the engine-drive pump as a working medium after the engine start-up, and additionally gear shifting can be made in a direction that the AMT is thrown out of the “starting-period shift-stage thrown state”, in other words, the “starting-period shift-stage thrown state” is canceled. In such a case, there is no possibility that the automotive vehicle begins to move against the driver's intention, simultaneously with the engine start-up.
In contrast, suppose that the previously-discussed AMT system failure that an automatic clutch remains engaged undesirably, has occurred. Under such an abnormal state (i.e., in the presence of the AMT system failure), the release of the automatic clutch, which uses working oil discharged from the engine-drive pump as a working medium, cannot be made, and thus the automatic clutch remains kept at its engaged state. Therefore, even if the previously-discussed gear shifting is made in a direction that the “starting-period shift-stage thrown state” is canceled, there is a possibility that the vehicle begins to move against the driver's intention during a time period (e.g., for a brief moment during the engine starting period) from the time when the gear shifting has terminated to the time when the AMT has been shifted to neutral. Such an abnormal situation where the vehicle begins to move against the driver's intention during the engine starting period, means a state where, even when the driver has no intention of moving the vehicle and thus the driver-selected operating range of the AMT is neutral (the N range), the vehicle begins to move against the driver's intention. The abnormal situation also means a state where, even when the driver has an intention of forward-traveling of the vehicle and thus the driver-selected operating range of the AMT is drive (the D range), the vehicle begins to move backward (i.e., in the reverse direction opposite to the direction based on the driver's intention). The abnormal situation also means a state where, even when the driver has an intention of reverse-traveling of the vehicle and thus the driver-selected operating range of the AMT is reverse (the R range), the vehicle begins to go ahead (i.e., in the forward direction opposite to the direction based on the driver's intention).
A vehicle control technology, which is useful in avoiding the previously-noted abnormal situation, has been proposed and disclosed in Japanese Patent Provisional Publication No. 62-122825 (hereinafter is referred to as “JP62-122825”). According to the technology disclosed in JP62-122825, prior to the engine start-up, a transmission is automatically shifted to neutral (exactly, a neutral range position) that disables the transmission to transmit power with all gears disengaged, or an automatic clutch is automatically released. In the case of the vehicle control device disclosed in JP62-122825, the former countermeasure is taken against a clutch system failure that the automatic clutch remains engaged undesirably. Concretely, in the presence of the clutch system failure that the automatic clutch remains engaged undesirably, prior to the engine start-up, (exactly, prior to engine cranking), the transmission is automatically shifted to neutral (the N range).